| Annona Chalk | |
| Type: | Sedimentary |
| Age: | Cretaceous |
| Period: | Cretaceous |
| Prilithology: | Chalk |
| Namedfor: | Annona, Red River County, Texas[1] |
| Namedby: | Robert Thomas Hill |
| Region: | Arkansas |
| Country: | United States |
| Subunits: | Austin Group |
| Underlies: | Marlbrook Marl |
| Overlies: | Ozan Formation |
| Thickness: | 30 Meters |
The Annona Chalk is a geologic formation in Arkansas, Texas, Louisiana, and Oklahoma.[2] It preserves fossils dating back to the Cretaceous period. The formation is a hard, thick-bedded to massive, slightly fossiliferous chalk. It weathers white, but is blue-gray when freshly exposed. The unit is commercially mined for cement. Fossils in the Annona Chalk include coelenterates, echinoderms, annelids, bivalves, gastropods, cephalopods, and some vertebrate traces.[3] The beds range in thickness, up to over 100 feet in depth in some areas (such as at White Cliffs).,[4] but thins to the east and is only a few feet thick north of Columbus, Arkansas and is completely missing to the east. The break between the Annona Formation and the Ozan Formation appears to be sharp with a few tubular borings up to a foot long extending down from the Annona in to the Ozan.[5]
B. crickmayi[6]
B. taylorensis[6]
D. binodosum[6]
D. clardyi[6]
N. (Nostoceras) danei[6]
N. (Nostoceras) monotuberculatum[6]
N. (Nostoceras) plerucostatum[6]
N. (Nostoceras) pulcher[6]
O. crassum[6]
A. ponderosana[7]
B. rotunda[7]
B. ovata[7]
B. windhami[7]
C. austinensis[7]
C. caudata[7]
C. communis[7]
C. filicosta[7]
C. paraustinensis[7]
C. crafti[7]
C. tollettensis[7]
C. blakei[7]
H. bruceclarki[7]
H. globosa[7]
H. micropunctata[7]
H. plummeri[7]
K. cushmani[7]
L. fletcheri[7]
M. montuosa[7]
M. pedata[7]
O. hannai[7]
P. texanus[7]
V. ozanana[7]